I'd vote POP.
I've stayed at both and I'd choose POP rooms over The Little Mermaid rooms. The LM rooms are on the outer edge of AoA so a bit of walk. At POP you have a lot more choice of where your room is.
Also, I will tell you that I am not the fan of AoA in general. I'm the type that is good with busy, whimisical, Disney bubble stuff and I've done multiple stays at the All Stars and POP, but I really disliked the atmosphere at AoA. It's really loud, really crowded and I never could relax there. But if you love any of those movies you might like it. And fair point that busy and crowede is to be expected because its a big draw for families and if that's a vibe you like then you might like it better.